Examples of hydraulically-actuated electronically-controlled unit injectors are shown in U.S. Pat. No. 3,689,205 issued to Links on Sep. 5, 1972, U.S. Pat. No. 3,796,205 issued to Links et al. on Mar. 12, 1974, and U.S. Pat. No. 3,835,829 issued to Links on Sep. 17, 1974. In each of these patents, a solenoid control valve is shown which controls the flow of actuating fluid to the unit injectors. The current state of the art in hydraulically-actuated electronically-controlled fuel injector systems are shown for example in U.S. Pat. No. 5,121,730, issued to Ausman et al. and U.S. Pat. No. 5,271,371, issued to Meints et al. In these patents, a solenoid controlled valve regulates injection by opening and closing to permit or stop the flow of pressurized actuating fluid to the unit injector. The actuating fluid serves to pressurize the fuel, which in turn causes injection for as long as pressurized actuating fluid is flowing into the unit injector. However, none of the above patents disclose how to accomplish rate shaping in hydraulically-actuated electronically-controlled fuel injectors nor recognize the consequences of constricting the flow of actuation fluid to the injector during a portion of each injection cycle.
The present invention is directed to introducing injection rate shaping to the art of hydraulically-actuated electronically-controlled fuel injection systems and to solve other problems encountered with the systems set forth above.